Many industries, and especially the textile industry, are constantly in search of new and improved methods of rendering materials soil resistant or for new soil resistant materials.
Soil repellancy is especially important in the textile industry to prolong the usefulness of material and increase the time interval in-between cleanings.
Many compounds, by themselves or as protective layers, have been tried to impart hydrophobic and oleophobic properties to materials. One of the more successful materials possessing these properties have been fluorine compounds. The greater the degree of fluorination the higher the hydrophobicity and oleophobicity. Unfortunately, for the textile industry, as the degree of fluorination of the synthetic material increases the material becomes less pliable and manageable. Highly fluorinated polymers can not be easily moulded and therefore the polymer itself finds limited use in the textile field.
Due to the problems existing with products formed from the polyfluorinated polymers itself, it was decided to cover synthetic or natural fibers with a polyfluorinated polymeric coating. The coating surface would then provide the necessary hydrophobic and oleophobic properties to the underlying material.
One disclosed means for the forming of a polyfluorinated polymeric film was to plasma polymerize a polyfluorinated unsaturated compound, such as perfluorobutane-2. The plasma was generated electrodelessly using plates excited at 13.56 MHz at 70 watts of power (a Plasmatic P.G. 100 watt generator was utilized). Millard et al, J. Applied Polymer Science, 17, 2501-2507 (1973). In this procedure a polymeric film was formed on glass and although the film showed soil repellancy properties, there was little adherency of the film to the glass.
In Plasma Polymerization, ACS Symposium Series No. 108, Pavlath et al, disclose a process for coating, by glow discharge plasma deposition, glass, synthetic polymers and wool with a polyfluoro coating. Once again deposition on glass showed little or no adhesion. Deposition on organic surfaces indicated a fluorocarbon-substrate graft. The source of the fluorocarbon was a polyfluorocarbon, such as perfluoroethylene, perfluoropropylene, perfluorobutane-2, and perfluoroethane. In all cases, solvent extraction of the coated material reduce the fluorine to carbon ratio, thus showing poor adhesion to the substrate. The initial deposition, when a polyfluorounsaturated source is utilized as the fluorocarbon, yielded a fluorine to carbon (F/C) ratio of 1.2:1 to 1.5:1 after about a 15 second treatment. This ratio, after extraction, was reduced to 0.2:1 to 0.3:1. When a polyfluorosaturated source is utilized as the fluorocarbon, an initial deposition having a F/C ratio of about 0.4:1 to 0.55:1, for wool, and 0.6:1 to 0.8:1 for polyethylene was obtained. Solvent extraction removed less fluorocarbon than for unsaturated compounds yielding a deposition having a F/C ratio of 0.4:1 to 0.55:1.
It is theorized that utilizing a polyfluorounsaturated compound as the fluorocarbon source, polymerization of the compounds occurs with weak adhesion between the polymer and substrate. When polyfluorosaturated compounds are utilized as the fluorocarbon source, there is less polymerization and the forming radicals interact with the substrate surface forming a stronger bond.
Millard et al, Textile Research Journal pages 307-313 (May 1972) discloses a continuous process, through low temperature discharge, for the coating of wool yarn to make said yarn soil resistant and shrink resistant. The fluorocarbon utilized was a fluorocarbon derivative of acrylic acid. As in previous cases, the surface coating had a weak interaction or adherence to the wool yarn and on solvent extraction half the coating was removed.